In the practice of orthodontics, orthodontic appliances such as brackets are typically secured directly to teeth using an adhesive bonding system. In the course of most orthodontic procedures, forces are applied to the orthodontic brackets by orthodontic archwires, which cause maloccluded teeth to move in a predetermined fashion. Thus, the bonding of orthodontic appliances to teeth is of critical importance for several reasons: 1) to ensure proper transfer of the forces directly to the teeth; 2) to ensure that no undue forces are exerted on the teeth, particularly during removal of the appliances, which may cause removal of enamel; and 3) to ensure that the appliances are not unintentionally debonded prior to the completion of the treatment.
With respect to orthodontic brackets having a metal bonding surface, various solutions have been suggested in the prior art to provide or enhance the bonding characteristics of the appliance. For example, U.S. Pat. Nos. 4,165,561 and 4,068,379 disclose the use of a metal mesh welded to the bonding base of the appliance in order to provide acceptable mechanical bonding characteristics. U.S. Pat. No. 4,927,361 suggests the use of particles in order to provide a porous structure on the tooth contact surface of the appliance. However, these types of brackets are made of materials which are substantially non-chemically reactive, and thus are limited with respect to the bond strengths that can be obtained since they rely on the mechanical bonding characteristics of the bracket.
With respect to non-metal brackets, e.g., brackets made of a ceramic material, bonding of the brackets generally incorporates the use of a chemical treatment so that high bond strengths between bracket and tooth are obtained. However, use of chemically reactive bonding adhesives generally requires special handling and care in order to obtain desired bonding strengths, as set forth in U.S. Pat. No. 4,681,538. Additionally, due to the high bond strengths obtained with ceramic-type brackets, and the manner in which the bonds are fractured, a much higher risk is presented that enamel may be removed from the tooth during bracket removal.
The present invention is intended to overcome the various drawbacks discussed above with respect to bonding brackets to teeth and encompasses improved orthodontic appliances and methods of making such appliances which result in improved bonding characteristics without presenting any substantially increased risk of removing enamel from the tooth.